BMR Calculator
Basal Metabolic Rate — calories burned at complete rest for basic bodily function — using three published formulas side by side.
Body
Optional (for Katch-McArdle)
BMR by Formula
Three formulas, three answers
Mifflin-St Jeor (1990): the current gold standard for most adults; validated against indirect calorimetry across large samples. Uses height, weight, age, and sex.
Harris-Benedict (revised 1984): the older classic. Slightly overestimates for most adults compared to Mifflin-St Jeor; still widely used in medical settings and reference tables.
Katch-McArdle (1996): uses lean body mass (weight minus fat mass) instead of total weight. Requires body fat percentage. Most accurate for athletes and very lean or very muscular people, where total-weight formulas over- or under-estimate.
When formulas disagree
For a typical 25–50-year-old adult in a normal BMI range, all three formulas produce numbers within ±100 kcal of each other. Larger disagreements suggest one formula is a poor fit for the individual — usually because the person is very muscular (Katch-McArdle beats the others), very obese (Mifflin-St Jeor most reliable), or elderly with sarcopenia (all formulas overstate; consider clinical measurement).